Flat panel displays have been developed and used in recent years as a display mechanism to rival the conventional cathode ray tube displays. Portable systems have benefitted from the use of flat panel displays as less space is required which allows for a lighter more compact system along with the fact the flat panel displays consume less power.
One type of flat panel display is the field emission cathode type wherein the electron emitting cathode is separated from the display face (or anode) at a relatively small and ideally uniform distance by an insulator. The insulation must be minimal and the number of cathodes high in order to obtain a display possessing the desirable features of high resolution and brightness.
As previously mentioned, a high number of cathodes is desirable in that better resolution is obtained. At the same time, if the spacing between cathode tips is uniform, the brightness will be uniform throughout the display. Unfortunately, as the number of tips increase, uniform spacing becomes increasingly difficult.
In U.S. Pat. No. 4,923,421, Brodie et al., a method for providing polyimide spacers in a field emission panel display is disclosed. In Brodie, the process comprises forming a insulating layer of polyimide material having uniform thickness over either the emission cathode or over the opposing display face in order to obtain a uniform distance between the two. Brodie, intentionally sandwiches the cathode and display face together in order to avoid the need of uniform spacing between the cathode and display face during fabrication.
In an article entitled "FABRICATION OF SILICON FIELD EMISSION POINTS FOR VACUUM MICROELECTRONICS BY WET CHEMICAL ETCHING", Semicond. Sci. Technology, Vol 6 (1991), pp 223-225, by Trujillo et al., various etching methods to sharpen field emission points are discussed. The main focus of this article is to fabricate the sharpest silicon emission tips possible in order to maximize field emission of electrons from cathode to the flat plane anode.
Also, in a technical article entitled "OXIDATION SHARPENING OF SILICON TIPS," J. Vac. Sci. Technol. B 9 (6), Nov./Dec. 1991, pp 2733-2737, by T.S. Ravi et al., a study describes unified etching/oxidation treatment that results in uniform tips with controlled radii of atomic dimensions. Variations in the etching/oxidation treatment cause multiple tips to form as discussed in this article.
These publications, however, fail to address the problem of how to maintain an array of evenly spaced-apart, self-aligned, cathode tips using conventional fabrication techniques.
The present invention, however, specifically teaches a simpler method to form self-aligned cathode emission tips as will be described.